Topic Contents

Iron for Sports & Fitness

Why Use

Why Do Athletes Use It?*

What Do the Advocates Say?*

Athletes are not at risk of developing iron deficiency or anemia any more than others; however, metabolically, athletes utilize more minerals, including iron, than non-athletes do.

Women have a greater risk of developing iron deficiency than men. Premenopausal women, in particular, are at risk of becoming iron-deficient because of the blood loss that occurs every month during menstruation.

Doctors often screen for iron deficiency by testing for anemia. However, individuals who have a mild deficiency of iron may not be anemic, since blood counts do not typically drop until iron stores in the body are almost completely depleted. If you suspect you are deficient in iron, ask your doctor to perform a more specific blood test, known as a "ferritin" test, rather than the routine "CBC" or "total iron" tests.

Prior to taking supplemental iron, people should be tested by a doctor to make sure such supplementation is appropriate. Although supplemental iron may help those who are deficient, too much iron may cause adverse side effects, including stomach and intestinal cramps, nausea, and constipation.

*Athletes and fitness advocates may claim benefits for this supplement based on their personal or professional experience. These are individual opinions and testimonials that may or may not be supported by controlled clinical studies or published scientific articles.

Dosage & Side Effects

Iron

How Much Is Usually Taken by Athletes?

Iron is important for an athlete because it is a component of hemoglobin, which transports oxygen to muscle cells. Some athletes, especially women, do not get enough iron in their diet. In addition, for reasons that are unclear, endurance athletes, such as marathon runners, frequently have low body-iron levels.1, 2, 3 However, anemia in athletes is often not due to iron deficiency and may be a normal adaptation to the stress of exercise.4 Supplementing with iron is usually unwise unless a deficiency has been diagnosed. People who experience undue fatigue (an early warning sign of iron deficiency) should have their iron status evaluated by a doctor. Athletes who are found to be iron deficient by a physician are typically given 100 mg per day until blood tests indicate they are no longer deficient. Supplementing iron-deficient athletes with 100 to 200 mg per day of iron increased aerobic exercise performance in some,5, 6, 7 though not all,8, 9 double-blind studies. A recent double-blind trial found that iron-deficient women who took 20 mg per day of iron for six weeks were able to perform knee strength exercises for a longer time without muscle fatigue compared with those taking a placebo.10

Side Effects

Caution: Iron (ferrous sulfate) is the leading cause of accidental poisonings in children.11, 12, 13 The incidence of iron poisonings in young children increased dramatically in 1986. Many of these children obtained the iron from a child-resistant container opened by themselves or another child, or left open or improperly closed by an adult.14 Deaths in children have occurred from ingesting as little as 200 mg to as much as 5.85 grams of iron.15 Keep iron-containing supplements out of a child's reach.

Hemochromatosis, hemosiderosis, polycythemia, and iron-loading anemias (such as thalassemia and sickle cell anemia) are conditions involving excessive storage of iron. Supplementing iron can be quite dangerous for people with these diseases.

Supplemental amounts required to overcome iron deficiency can cause constipation. Sometimes switching the form of iron (see "Which forms of supplemental iron are best?" above), getting more exercise, or treating the constipation with fiber and fluids is helpful, though fiber can reduce iron absorption (see below). Sometimes the amount of iron must be reduced if constipation occurs.

Some researchers have linked excess iron levels to diabetes,16cancer,17 increased risk of infection,18systemic lupus erythematosus (SLE),19 exacerbation of rheumatoid arthritis,20 and Huntington's disease.21 The greatest concern has surrounded the possibility that excess storage of iron in the body increases the risk of heart disease.22, 23, 24 Two analyses of published studies came to different conclusions about whether iron could increase heart disease risk.25, 26 One trial has suggested that such a link may exist, but only in some people (possibly smokers or those with elevated cholesterol levels).27 The link between excess iron and any of the diseases mentioned earlier in this paragraph has not been definitively proven. Nonetheless, too much iron causes free radical damage, which can, in theory, promote or exacerbate most of these diseases. People who are not iron deficient should generally not take iron supplements.

Patients on kidney dialysis who are given injections of iron frequently experience "oxidative stress". This is because iron is a pro-oxidant, meaning that it interacts with oxygen molecules in ways that can damage tissues. These adverse effects of iron therapy may be counteracted by supplementation with vitamin E.28

Supplementation with iron, or iron and zinc, has been found to improve vitamin A status among children at high risk for deficiency of the three nutrients. 29

People with hepatitis C who have failed to respond to interferon therapy have been found to have higher amounts of iron within the liver. Moreover, reduction of iron levels by drawing blood has been shown to decrease liver injury caused by hepatitis C.30 Therefore, people with hepatitis C should avoid iron supplements.

Interactions with Supplements, Foods, & Other Compounds

Many foods, beverages, and supplements have been shown to affect the absorption of iron.32

Foods, beverages and supplements that interfere with iron absorption include

Green tea(Camellia sinensis).33, 34, 35, 36 This effect may be desirable for people with iron overload diseases, such as hemochromatosis. The inhibitory effect of green tea on iron absorption was 26% in one study.37

Coffee (Coffea arabica, C. robusta).38, 39, 40

Red wine, particularly the polyphenol component (also found in tea).41, 42 Since wine is also a dietary source of iron, it is not clear whether drinking red wine would lead to a deficiency of iron.

Phytate (phytic acid), found in unleavened wheat products such as matzoh, pita, and some rye crackers; in wheat germ, oats, nuts, cacao powder, vanilla extract, beans, and many other foods, and in IP-6 supplements.43, 44, 45

Whole wheat bran, independent of its phytate content, has been shown to inhibit iron absorption.46

Calcium from food and supplements interferes with heme-iron absorption.47, 48

Alcohol, but not red wine, has been reported to increase the absorption of ferric, but not ferrous, iron.67, 68

Iron has been reported to potentially interfere with manganese absorption. In one trial, women with high iron status had relatively poor absorption of manganese.69 In another trial studying manganese/iron interactions in women, increased intake of "non-heme iron"-the kind of iron found in most supplements-decreased manganese status.70 These interactions suggest that taking multiminerals that include manganese may protect against manganese deficiencies that might otherwise be triggered by taking isolated iron supplements.

Interactions with Medicines

Replenish Depleted Nutrients

Gastrointestinal (GI) bleeding is a common side effect of taking aspirin. A person with aspirin-induced GI bleeding may not always have symptoms (like stomach pain) or obvious signs of blood in their stool. Such bleeding causes loss of iron from the body. Long-term blood loss due to regular use of aspirin can lead to iron-deficiency anemia. Lost iron can be replaced with iron supplements. Iron supplementation should be used only in cases of iron deficiency verified with laboratory tests.

Stomach acid may facilitate iron absorption. H-2 blocker drugs reduce stomach acid and are associated with decreased dietary iron absorption.73 People with ulcers may also be iron deficient due to blood loss and benefit from iron supplementation. Iron levels in the blood can be checked with lab tests.

Some studies suggest the taking of too much iron by individuals who are not iron deficient can result in tissue damage that may contribute to heart disease.74 Test tube studies have shown dipyridamole blocks platelet clumping caused by iron,75 which might reduce the damage caused by this mineral. Controlled human studies are needed to test this possibility.

NSAIDs cause gastrointestinal (GI) irritation, bleeding, and iron loss.77 Iron supplements can cause GI irritation.78 However, iron supplementation is sometimes needed in people taking NSAIDs if those drugs have caused enough blood loss to lead to iron deficiency. If both iron and etodolac are prescribed, they should be taken with food to reduce GI irritation and bleeding risk.

Stomach acid may increase absorption of iron from food. H-2 blocker drugs reduce stomach acid and are associated with decreased dietary iron absorption.79 The iron found in supplements is available to the body without the need for stomach acid. People with ulcers may be iron deficient due to blood loss. If iron deficiency is present, iron supplementation may be beneficial. Iron levels in the blood can be checked with lab tests.

NSAIDs cause gastrointestinal (GI) irritation, bleeding, and iron loss.82 Iron supplements can cause GI irritation.83 However, iron supplementation is sometimes needed in people taking NSAIDs if those drugs have caused enough blood loss to lead to iron deficiency. If both iron and ibuprofen are prescribed, they should be taken with food to reduce GI irritation and bleeding risk.

Antacids, including magnesium hydroxide, may reduce the absorption of dietary iron. Iron supplements do not require stomach acid for absorption and one human study found that a magnesium hydroxide/aluminum hydroxide antacid did not decrease supplemental iron absorption.85

NSAIDs cause gastrointestinal (GI) irritation, bleeding, and iron loss.87 Iron supplements can cause GI irritation.88 However, iron supplementation is sometimes needed in people taking NSAIDs if those drugs have caused enough blood loss to lead to iron deficiency. If both iron and nabumetone are prescribed, they should be taken with food to reduce GI irritation and bleeding risk.

NSAIDs cause gastrointestinal (GI) irritation, bleeding, and iron loss.89 Iron supplements can cause GI irritation.90 However, iron supplementation is sometimes needed in people taking NSAIDs if those drugs have caused enough blood loss to lead to iron deficiency. If both iron and naproxen are prescribed, they should be taken with food to reduce GI irritation and bleeding risk.

Stomach acid may increase absorption of iron from food. H-2 blocker drugs reduce stomach acid and are associated with decreased dietary iron absorption.93 The iron found in supplements is available to the body without the need for stomach acid. People with ulcers may be iron deficient due to blood loss. If iron deficiency is present, iron supplementation may be beneficial. Iron levels in the blood can be checked with lab tests.

NSAIDs cause gastrointestinal (GI) irritation, bleeding, and iron loss.94 Iron supplements can cause GI irritation.95 However, iron supplementation is sometimes needed in people taking NSAIDs if those drugs have caused enough blood loss to lead to iron deficiency. If both iron and oxaprozin are prescribed, they should be taken with food to reduce GI irritation and bleeding risk.

Stomach acid may facilitate iron absorption. H-2 blocker drugs reduce stomach acid and are associated with decreased dietary iron absorption.99 People with ulcers may also be iron deficient due to blood loss and benefit from iron supplementation. Iron levels in the blood can be checked with lab tests.

In a study of nine healthy people, sodium bicarbonate administered with 10 mg of iron led to lower iron levels compared to iron administered alone.100 This interaction may be avoided by taking sodium bicarbonate-containing products two hours before or after iron-containing supplements.

Stanozolol was associated with iron depletion in a group of 16 people.101 The results suggest that people taking this drug on a regular basis have their iron status monitored by the prescribing doctor. There is insufficient information to recommend routine iron supplementation during stanozolol treatment.

Reduce Side Effects

In a double-blind study of patients who had developed a cough attributed to an ACE inhibitor, supplementation with iron (in the form of 256 mg of ferrous sulfate per day) for four weeks reduced the severity of the cough by a statistically significant 45%, compared with a nonsignificant 8% improvement in the placebo group.71

In a double-blind study of patients who had developed a cough attributed to an ACE inhibitor, supplementation with iron (in the form of 256 mg of ferrous sulfate per day) for four weeks reduced the severity of the cough by a statistically significant 45%, compared with a nonsignificant 8% improvement in the placebo group.72

In a double-blind study of patients who had developed a cough attributed to an ACE inhibitor, supplementation with iron (in the form of 256 mg of ferrous sulfate per day) for four weeks reduced the severity of the cough by a statistically significant 45%, compared with a nonsignificant 8% improvement in the placebo group.76

In a double-blind study of patients who had developed a cough attributed to an ACE inhibitor, supplementation with iron (in the form of 256 mg of ferrous sulfate per day) for four weeks reduced the severity of the cough by a statistically significant 45%, compared with a nonsignificant 8% improvement in the placebo group.80

In a double-blind study of patients who had developed a cough attributed to an ACE inhibitor, supplementation with iron (in the form of 256 mg of ferrous sulfate per day) for four weeks reduced the severity of the cough by a statistically significant 45%, compared with a nonsignificant 8% improvement in the placebo group.84

In a double-blind study of patients who had developed a cough attributed to an ACE inhibitor, supplementation with iron (in the form of 256 mg of ferrous sulfate per day) for four weeks reduced the severity of the cough by a statistically significant 45%, compared with a nonsignificant 8% improvement in the placebo group.86

In a double-blind study of patients who had developed a cough attributed to an ACE inhibitor, supplementation with iron (in the form of 256 mg of ferrous sulfate per day) for four weeks reduced the severity of the cough by a statistically significant 45%, compared with a nonsignificant 8% improvement in the placebo group.96

In a double-blind study of patients who had developed a cough attributed to an ACE inhibitor, supplementation with iron (in the form of 256 mg of ferrous sulfate per day) for four weeks reduced the severity of the cough by a statistically significant 45%, compared with a nonsignificant 8% improvement in the placebo group.97

In a double-blind study of patients who had developed a cough attributed to an ACE inhibitor, supplementation with iron (in the form of 256 mg of ferrous sulfate per day) for four weeks reduced the severity of the cough by a statistically significant 45%, compared with a nonsignificant 8% improvement in the placebo group.98

In a double-blind study of patients who had developed a cough attributed to an ACE inhibitor, supplementation with iron (in the form of 256 mg of ferrous sulfate per day) for four weeks reduced the severity of the cough by a statistically significant 45%, compared with a nonsignificant 8% improvement in the placebo group.102

Minerals such as aluminum, calcium, copper, iron, magnesium, manganese, and zinc can bind to ciprofloxacin, greatly reducing the absorption of the drug.105, 106, 107, 108 Because of the mineral content, people are advised to take ciprofloxacin two hours after consuming dairy products (milk, cheese, yogurt, ice cream, and others), antacids (Maalox®, Mylanta®, Tums®, Rolaids®, and others), and mineral-containing supplements.109

Taking mineral supplements or antacids that contain aluminum, calcium, iron, magnesium, or zinc at the same time as tetracyclines inhibits the absorption of the drug.110 Therefore, individuals should take tetracyclines at least two hours before or after products containing minerals.

Many minerals can decrease the absorption and reduce effectiveness of doxycycline, including calcium, magnesium, iron, zinc, and others.111 To avoid these interactions, doxycycline should be taken two hours before or two hours after dairy products (high in calcium) and mineral-containing antacids or supplements.

A review of interactions involving quinolone antibiotics indicated that supplements containing iron, when taken at the same time as gemifloxacin, might reduce absorption of the drug up to 50%.112 Consequently, gemifloxacin and supplements containing iron should not be taken at the same time.

Taking iron supplements concomitantly with levofloxacin can reduce the absorption-and thus the effectiveness-of the drug.115 Therefore, nutritional supplements containing iron, if used, should be taken two hours before or after taking levofloxacin.

Iron supplements may decrease absorption of thyroid hormone medications.116, 117 People taking thyroid hormone medications should talk with their doctor before taking iron-containing products. If advised to supplement, iron and the drug should not be taken within less than four hours of each other.

Taking calcium, iron, magnesium, or zinc at the same time as minocycline can decrease the absorption of both the drug120, 121 and the mineral. Therefore, calcium, iron, magnesium, or zinc supplements, if used, should be taken an hour before or after the drug.

Minerals including calcium, iron, magnesium, and zinc can bind to fluoroquinolones, including ofloxacin, greatly reducing drug absorption.122 Ofloxacin should be taken four hours before or two hours after consuming antacids (Maalox®, Mylanta®, Tumms®, Rolaids® and others) that may contain these minerals and mineral-containing supplements.123

Penicillamine binds iron. When taken with iron, penicillamine absorption and activity are reduced.124 Four cases of penicillamine-induced kidney damage were reported when concomitant iron therapy was stopped, which presumably led to the increased penicillamine absorption and toxicity.125

Taking risedronate at the same time as iron, zinc, or magnesium may reduce the amount of drug absorbed.126 Therefore, people taking risedronate who wish to supplement with these minerals should take them an hour before or two hours after the drug.

Iron can bind with sulfasalazine, decreasing sulfasalazine absorption and possibly decreasing iron absorption.127 This interaction can be minimized by taking iron-containing products two hours before or after sulfasalazine.

Iron, magnesium, and zinc may bind with warfarin, potentially decreasing their absorption and activity.128 People on warfarin therapy should take warfarin and iron/magnesium/zinc-containing products at least two hours apart.

Potential Negative Interaction

People treated with deferoxamine for dangerously high levels of iron should not take iron supplements, because iron exacerbates their condition, further increasing the need for the deferoxamine. They should read all labels carefully for iron content. All people treated with deferoxamine should consult their prescribing doctor before using any iron-containing products.

Iron supplements can cause stomach irritation. Use of iron supplements with indomethacin increases the risk of stomach irritation and bleeding.114 However, stomach bleeding causes iron loss. If both iron and indomethacin are prescribed, they should be taken with food to reduce stomach irritation and bleeding risk.

Explanation Required

Iron may interfere with captopril absorption. They should not be taken within two hours of each other.129

In a double-blind study of patients who had developed a cough attributed to an ACE inhibitor, supplementation with iron (in the form of 256 mg of ferrous sulfate per day) for four weeks reduced the severity of the cough by a statistically significant 45%, compared with a nonsignificant 8% improvement in the placebo group.130

Menstrual blood loss is typically reduced with use of oral contraceptives. This can lead to increased iron stores and, presumably, a decreased need for iron in premenopausal women.131 Premenopausal women taking oral contraceptives should have their iron levels monitored and talk with their prescribing doctor before using iron-containing supplements.

Iron deficiency has been reported to impair the body's ability to make its own thyroid hormones,132 which could increase the need for thyroid medication. In a preliminary trial, iron supplementation given to iron-deficient women with low blood levels of thyroid hormones, partially normalized these levels.133 Diagnosing iron deficiency requires the help of a doctor. The body's ability to make its own thyroid hormones is also reduced during low-calorie dieting. Iron supplementation (27 mg per day) was reported in a controlled study to help maintain normal thyroid hormone levels in obese patients despite a very low-calorie diet.134

However, iron supplements may decrease absorption of thyroid hormone medications.135, 136 People taking thyroid hormone medications should talk with their doctor before taking iron-containing products. If advised to supplement, iron and the drug should not be taken within less than four hours of each other.

Menstrual blood loss is typically reduced with use of oral contraceptives. This can lead to increased iron stores and, presumably, a decreased need for iron in premenopausal women.137 Premenopausal women taking oral contraceptives should have their iron levels monitored and talk with their prescribing doctor before using iron-containing supplements.

Menstrual blood loss is typically reduced with use of OCs. This can lead to increased iron stores and, presumably, a decreased need for iron in premenopausal women.138 Premenopausal women taking OCs should have their iron levels monitored and talk with their prescribing doctor before using iron-containing supplements.

Menstrual blood loss is typically reduced with use of OCs. This can lead to increased iron stores and, presumably, a decreased need for iron in premenopausal women.139 Premenopausal women taking OCs should have their iron levels monitored and talk with their prescribing doctor before using iron-containing supplements.

Menstrual blood loss is typically reduced with use of oral contraceptives. This can lead to increased iron stores and, presumably, a decreased need for iron in premenopausal women.140 Premenopausal women taking oral contraceptives should have their iron levels monitored and talk with their prescribing doctor before using iron-containing supplements.

Menstrual blood loss is typically reduced with use of oral contraceptives. This can lead to increased iron stores and, presumably, a decreased need for iron in premenopausal women.141 Premenopausal women taking oral contraceptives should have their iron levels monitored and talk with their prescribing doctor before using iron-containing supplements.

Menstrual blood loss is typically reduced with use of oral contraceptives. This can lead to increased iron stores and, presumably, a decreased need for iron in premenopausal women.142 Premenopausal women taking oral contraceptives should have their iron levels monitored and talk with their prescribing doctor before using iron-containing supplements.

Iron deficiency has been reported to impair the body's ability to make its own thyroid hormones,143 which could increase the need for thyroid medication. In a preliminary trial, iron supplementation given to iron-deficient women with low blood levels of thyroid hormones, partially normalized these levels.144 Diagnosing iron deficiency requires the help of a doctor. The body's ability to make its own thyroid hormones is also reduced during low-calorie dieting. Iron supplementation (27 mg per day) was reported in a controlled study to help maintain normal thyroid hormone levels in obese patients despite a very low-calorie diet.145

However, iron supplements may decrease absorption of thyroid hormone medications.146, 147 People taking thyroid hormone medications should talk with their doctor before taking iron-containing products. If advised to supplement, iron and the drug should not be taken within less than four hours of each other.

Iron deficiency has been reported to impair the body's ability to make its own thyroid hormones,148 which could increase the need for thyroid medication. In a preliminary trial, iron supplementation given to iron-deficient women with low blood levels of thyroid hormones, partially normalized these levels.149 Diagnosing iron deficiency requires the help of a doctor. The body's ability to make its own thyroid hormones is also reduced during low-calorie dieting. Iron supplementation (27 mg per day) was reported in a controlled study to help maintain normal thyroid hormone levels in obese patients despite a very low-calorie diet.150

However, iron supplements may decrease absorption of thyroid hormone medications.151, 152 People taking thyroid hormone medications should talk with their doctor before taking iron-containing products. If advised to supplement, iron and the drug should not be taken within less than four hours of each other.

Iron deficiency has been reported to impair the body's ability to make its own thyroid hormones,153 which could increase the need for thyroid medication. In a preliminary trial, iron supplementation given to iron-deficient women with low blood levels of thyroid hormones, partially normalized these levels.154 Diagnosing iron deficiency requires the help of a doctor. The body's ability to make its own thyroid hormones is also reduced during low-calorie dieting. Iron supplementation (27 mg per day) was reported in a controlled study to help maintain normal thyroid hormone levels in obese patients despite a very low-calorie diet.155

However, iron supplements may decrease absorption of thyroid hormone medications.156, 157 People taking thyroid hormone medications should talk with their doctor before taking iron-containing products. If advised to supplement, iron and the drug should not be taken within less than four hours of each other.

Menstrual blood loss is typically reduced with use of oral contraceptives. This can lead to increased iron stores and, presumably, a decreased need for iron in premenopausal women.158 Premenopausal women taking oral contraceptives should have their iron levels monitored and talk with their prescribing doctor before using iron-containing supplements.

Menstrual blood loss is typically reduced with use of OCs. This can lead to increased iron stores and, presumably, a decreased need for iron in premenopausal women.159 Premenopausal women taking OCs should have their iron levels monitored and talk with their prescribing doctor before using iron-containing supplements.

More Resources

Iron

Where to Find It

The most absorbable form of iron, called "heme" iron, is found in oysters, meat and poultry, and fish. Non-heme iron is also found in these foods, as well as in dried fruit, molasses, leafy green vegetables, wine, and iron supplements. Acidic foods (such as tomato sauce) cooked in an iron pan can also be a source of dietary iron.

The information presented in Aisle7 is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires June 2016.

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